Electrical ignition device



July 9, 1935. L.. s. cHADwlcK ET AL 2,007,889

ELECTRICAL IGNITION DEVICE Filed Aug. 27, 1930 4 Sheets-Sheet, l

iu KLM July 9, 1935- l.. s. cHADwlcK Er Al. 2,007,889

ELECTRICAL lGNITION DEVICE Filed Aug. 27, 1930 4 Sheets-Sheet 2 July 9, 1935. 1 s. cHADwxcK ET AL 2,007,889

ELECTRICAL IGNITION DEVICE Filed Aug. 27, 1950 4 Sheets-Sheet 3 July 9, 1935.

L. S. CHADWICK El AL ELECTRICAL IGNITION DEVICE Filed Aug. 27, 1930 4 Sheetssheet 4 Patented' July 9, 1935 l UNITED STATES PATENT OFFICE Alger Dahlstrom, Bay

Village, and Arthur John Wiltshire, Cleveland, Ohio, assignors to Perfection Stove Company, Cleveland, Ohio, a corporation of Ohio Application August 27,

16 Claims.

This invention relates to an electrical ignition device for use with oil burners, particularly of the class in which-the oil is projected in a'thin sheet or spray, the device being of the hot wire or hot element type (as distinguished from the spark type).

Devicesof the kind referred to are subjected to intense heat-both that generated within themselves during the ignition period, and that of the burner flame when thevburner is in operation-and unless provisions are made for preventing it, the devices tend toward rapid deterioration. A further destructive agent to which such devices are exposed is the sulphur that is frequently present in the fuel oil. v

It is the primary purpose of our invention, therefore, to provide a durable electrical ignition device that will withstand high temperatures and the effects of sulphur for a very considerable length of time.

Further objects are to provide a device of the above character that is highly efficient, that is simple of construction, that is economical of manufacture, and that involves a relatively cheap heating element that may be readily removed and replaced by a fresh one in case the element becomes deficient or unserviceable through long continued use; and to provide an electrical ignition device wherein the terminal connections of the ignition element are of a simple but highly effective nature, requiring no manipulations but the mere slipping of the terminals -into socketlikereceivers; in which such receivers preferably consist of mercury wells into which the terminals dip; and wherein such receivers or mercury wells are located in a convenient position to receive the terminals of the element but where they will be air cooled by the draft induced by the burner and thus protected from the heat.

An embodiment of the invention through which the foregoing objects are attained is illustrated in the accompanying drawings wherein Fig. l is a. sectional side elevation of a rotary oil burner equipped with our improved ignition device; Fig. 2 is a vertical section through the ignition device on a scale considerably enlarged over that of Fig. 1; Fig. 3 is a vertical transverse section on the line 3-3 of Fig. 2; Fig. 4 is a sectional detail on the lines 4--4 of Figs. 2 and 3; Fig. 5 is a perspective view of the ignition element; Fig. 6 is a similar view of the guide block for the terminal posts of the element; Fig. 7 is a sectional detail of' one of the mercury wells closed by a. plug that is intended to be removed after the burner has been installed preparatory to emplacing the 1930, Serial No. 478,140

ignition element; and Fig. 8 is a diagram showing the ignition circuit and the transformer therein.

I Although our invention is applicable to various types of burnersl we have elected to show it in the present instance in connection with an oil burning apparatus in which the oil is hurled in a horizontal spray or sheet outwardly across a hearth toward an upstanding peripheral wall thereof by means of a fuel delivery cup when the latter is rotated at a suitable speed by means of an electric motor. The particular burner herein disclosedis that constituting the subject matter of an application filed July 27, 1929, jointly by Lee S. Chadwick and John Alger Dahlstrom, two of the present applicants, and one Marc Resek, the same bearing Serial No. 381,600 now Patent Number 1,911,264, May 30, 1933. As shown in Fig. 1 hereof, the burner consists, generally, of a cup I that is supported for rotation by the vertically disposed shaft of an electric motor 2. The cup has a depending sleeve 3 which dips into an oil reservoir 4 that is supplied with oil, to a given height, through a pipe 5. The oil level may be controlled by a float mechanism in a tank from which the pipe 5 leads, but inasmuch as this is a well known expedient and constitutes no part of the present invention it is deemed unnecessary to illustrate the same. As above stated, the sleeve 3 dips into the body of oil in the reservoir 4, and as the cup spins the oil is caused to travel upwardly along said sleeve and through openings 'I into the interior of the cup where it ascends the wall of the cup and is hurled from the rim thereof across the hearth I0. Air is drawn upwardly about the cup by a fan II and is thrown outwardly with the oil, andthe resultant mixture is ignited by the electrical ignition device of our present invention.

The motor 2 and the reservoir 4 are enclosed, respectively, by casing sections I5 and I6 whose interiors communicate through one or more openings II ina horizontal wall that separates the casing sections and from which the motor 2 is suspended and whereon the reservoir 4 is mounted. The upperl end of the casing section I6 joins a hearth plate or pan I8 on which the hearth proper, designated I0, rests. The hearth consists of a horizontal portion or bottom wall and a peripheral wall I 9 that rises from the edge thereof. The inner surface of the peripheral wall is inclined upwardly and outwardly from the top surface of the bottom wall, and in the horizontal plane of the rim of the cup I the peripheral wall I9 is provided with a circumferential groove 20. 'This groove is an important factor in the successful operation of the burner as it insures a proper mixing of the air and oil,

at the zone of combustion.

All air for the promotion of combustion is supplied through an air duct 23 that is made up of telescoping sleeve sections 2| and 22, the inner end of the sleeve section 2| being extended through and fitting within an opening in the peripheral wall of the casing section l5. When installed, the burner assembly, consisting of the parts above described, is supported by legs 24 within the ash pit 25 of a furnace 26, the parts being so proportioned that therhearth of the burner is disposed within the bottom of the combustion chamber or iirebox 21. The door opening of the ash pit is closed by a plate 28 through which thesleeve section 23 extends, and adjustably connected to the forward end of said sleeve section, by means of slotted tongues 29 Vand bolts 29, is a damper unit 30. A cylindrical screen 3| is carried bythe damper unit and iitswithin the outer end'of the air duct to prevent the entrance of pieces of foreign matter of appreciable size. l'

The heating or ignition element of our improved ignition device, and which is designated 32 in the drawings, consists of a U-shaped wire resistor whose ends are bent at an acute angle to the plane of its body portion and are inserted into axial bores in the ends of terminal posts 33 that are formed of rods of suitable length andv diameter, the ends of the resistor 32 being preferably welded at 35 to the rods so as to eiect a strong mechanical and good electrical connection between the parts. The element 32 has a high electrical resistance and a high resistance to derefractoryinsulating material that will withstandV the intense heat of the burner flame, and saidL guide block is shown as secured in place by screws 38 that are engaged through apertures in an ear 39 that is struck downwardly from the burner plate or pan I8 and are threaded into-the guide block, the guide block passing through the opening from which said ear is struck. As shown particularly in Figs. l and 3, the resistor 32 re-v portance as it prevents the free passage of the combustible mixture and the products of combustion about the wirel resistor, thereby protecting it from the deteriorating effects thereof, as

`otherwise the wire would be completely enveloped by and subjected to the destructive influences of the burning oil. By reasn of this construction, therefore, the life of the resistor is greatly prolonged.

Fitted within an. opening in the top of the` axis, are mercury wells 43, and' in line with each p well is a threaded bore 44 that opens lthrough the top of the block, the same being shown as counterbored'at 45 for a purpose. which will presently appear, Suitably connected to the lowduct 23 through insulating bushings 41 that are fitted within openings in the damper unit 30. The inner ends of the lead wires are shown, in the present instance, as clamped within tapered recesses 48 of the mercury wells by contacting frusto-conical chuck members 49 that are forced into the recesses by clamping nuts 50. A quantity of mercury, designated 5|, is contained in each of the wells 43. The terminal posts 33 of the ignition element extend downwardly through the bores 44 into the mercury wells 43 to a point near the bottoms thereof. Thus a very intimate electrical connection is formed between the lead wires 46 and the terminal posts of the ignition element through the medium of the mercury wells.

When it becomes necessary to replace the ignition element, the same may be lifted so as to Withdraw the terminal posts 33 from the mercury wells and retract them upwardly through the bores of the guide block 31, and a fresh element may then be emplaced by inserting its terminal posts through the bores of the guide block which will direct their lower ends into the counterbores 45 of the block 42, and the inclined bottom walls of said counterbores will guide the posts through the bores 44 into'the mercury wells.

Upon completion of the manufacture of a burner equipped with our improved ignition device, a given' quantity of mercury is poured into each of the mercury wells 43 and the well is closed by a plug 52 that is threaded into the corresponding bore 44, as shown in Fig. '7. After the burner is installed, the plugs 52 are removed and the ignition element is inserted in the manner above described.

The invention is suitable for use with various types of burners of the general class herein disclosed, either alone or in conjunction with electrical control systems for rendering such'burners automatic; and the supply of current to the ignition device may be controlled by any suitable means. It may be explained, however, that in order to heat a wire, such as that constituting the ignition element-or resistor, to a high temperature, itis necessary that the current flow be high. In the attainment of this high flow of current-in order to keep the power consumption at a minimumit is customary to use a very low voltage. .So as to have a high current and low voltage it is, of course, essential thatV the resistance in the circuit bevery low. This is accomplished by means of a step-down transformer which reduces the usual volt, 60 cycle alternating current to a very low voltage in a low resistance secondary circuit. As the heat produced in the ignition element is proportional to the square of the current, it is evident that a slight variation in the current produces considerable variation in the temperature of the ignition element, and this, in case the current is low, results in too low a temperature for satisfactory ignition, or, in case thev current is high, in so high a temperature that the ignition element is destroyed. Variation in the current is ordinarily caused either by fluctuations in the line voltage or by change in resistance of the ignition element, as by an accumulation of carbon thereon.

`In order to prevent fluctuations in the current, we employ, in place of an ordinary step-down transformer, one that is known as a constant current step-down transformer. Such devices are well known in the electrical art wherever it is desiredrto hold a currentI constant under changing load conditions or fiuctuating voltage and, as diagrarnmatically shown in Fig. 8, the same comprises two coils, vto wit: a secondary coil 55 and a primary coil 56, the former of which is stationary vwhile the other is free to move. As a consequence of this, when current is flowing in the secondary coil 55 of the transformer the coils repel each other and are forced apart by this electromagnetic repulsion. In our device the primary coil 56 is connected to a source of current and is arranged so that it is free to move on the center post 51 of the transformer core 58, and the secondary coil 55, which is of low resistance and of the proper number of turns vto produce the desired current and voltage, is rigidly fastened to the core. The primary coil 56 is in circuit with the source of current, designated Line in Figs. 1 and 8, through conductors 59 and control means 60, the latter consisting of or including a suitable switch (not shown) and the secondary coil is electrically connected to the lead Wires 46 so that when the primary circuit is closed a suitable current for heating the ignition element 32 is induced in the secondary circuit and this current remains at practically constant value regardless of fluctuations in the voltage of the primary circuit or variations in the resistance of the ignition element, changes in voltage or resistance merely producing a lgreater or less repulsion between the primary and the secondary coils.

Having thus described our invention, what we claim is:

1. For use with burners of the class having means for projecting a spray of oil; an electrical ignition device comprising mercury wells adapted to be disposed below the plane of the oil spray and beyond the heat of combustion, electrical conductors connected therewithy and an ignition element adapted to be positioned in igniting relation to the sprayed oil and having terminals projecting into the mercury wells.

2. For use with burners of the class incorporating a hearth and means for projecting a spray of oil across the same; an electrical ignition device comprising a guide adapted to be set within the hearth, mercury wells arranged to be disposed below the plane of the hearth and beyond the heat of combustion, electrical conductors connected to the mercury wells, and an ignition element having terminal posts slidably projected through said guide and dipping into the mercury wells.

3. For use with burners of the class having means for drawing in air and proecting it with a spray of oil into the zone of combustion; an electrical ignition device comprising mercury wells arranged to be subjected to the current of incoming air and thus protected from the heat of combustion, means for connecting electrical conductors to said wells, and an ignition element .adapted to be disposed in igniting relation to the. sprayed oil and having terminals that dip into the mercury Wells.

4. For use with burners of the class incorporating an air duct, together with means for drawing air through said duct and projecting it with a spray of oil into the zone of combustion; an electrical ignition device comprising mercury wells adapted to be located in the air duct and thus protected from the heat of combustion,

igniting relation to the sprayed oil and having terminals that project into the mercury wells.

5. For use with burners of the class incorporating a hearth and an enclosed air duct spaced therebelow, together with means for drawing air through said duct and projecting it with a spray of oil across the hearth; an electrical ignition device comprising mercury wells adapted to be supported within the air duct, electrical conductors connected to said wells, a guide arranged to be set within the hearth, and an ignition element adapted to be disposed above the hearth in igniting relation to the sprayed oil and having terminal posts slidably projected through the guide and dipping into the mercury wells.

6. For use with burners of the class incorporating an air duct, together with means for drawing air through said duct and projecting it with a spray of oil into the zone of combustion; in combination with a part of said duct having an opening in its wall, a unit extending across said opening and insulated from the wall o! the duct and incorporating mercury Wells that are insulated from each other, electrical conductors connected to the mercury wells, and an ignition element adapted to be positioned in igniting relation to the sprayed oil and having terminals projecting into the mercury wells.

7. For use with burners of the class incorporating an air duct, together with means for drawing air through said duct and projecting it with a spray of oil into the zone of combustion; in combination with a part of said duct having an opening in its wall, an electrical ignition device comprising a block of insulating material extending across said opening, mercury wells depending from said block, the block having bores leading into the mercury wells, electrical conductors connected to the mercury wells, and an ignition element adapted to be positioned in igniting relation to the sprayed oil and having terminals projecting through the bores in the block and into the mercury wells.

8. For use with burners of the class incorporating an air duct, together with means for drawing air through said duct and projecting it with a spray of oil into the zone of combustion; in combination with a part of said duct having an opening in its wall, an electrical ignition device comprising a block of insulating material extending across said opening, mercury wells depending from said block, the block having bores leading into the mercury wells, electrical conductors connected to the mercury wells, and an ignition element adapted to be positioned in igniting relation to the sprayed oil and having terminals projecting through the bores in the block into the mercury wells, the bores of said block being ar ranged to receive plugs in the absence of said terminals.

9. For use with burners of the class incorporating an air duct, together with means for drawing air through said duct and projecting it with a spray of oil into the zone of combustion; in combination with a part of said duct having an opening in its wall, an electrical ignition device comprising a block of insulating material extending across said opening, mercury wells depending from said block, the block having bores leading into the mercury wells, electrical conductors connected to the mercury wells, and an ignition element adapted to be positioned in igniting relation to the sprayed oil and having terminals projecting through the bores in the block and into the mercury wells, the bores of said block beingJ threaded vfor the reception of closing plugs in the absence of said terminals.

10. For use with burners of the class incorporating a hearth and an air duct therebelow, together with means for drawing air through said duct, and projecting it with a spray of oil across the'hearth, in combination with parts of the hearth and air duct that are provided with openings, an electrical ignition device comprising a guide block supported Within the opening of the hearth, 49, well supporting block extending across theopening of the air duct, mercury wells depending from the last mentioned block, both blocks having substantially axially aligned bores in line with each of the mercury wells, those of the second 'mentioned block opening into said wells, and an ignition elementl arranged to be disposed in igniting relation to the sprayed oil and having terminal posts that 1extend through the bores of said blocks and into the mercury wells, said terminals being freely withdrawable.

from the mercury wells vand said bores.

11. For use with burners of the class incorporating means for producing an oil spray; an electrical ignition device comprising Amercury Wells adapted to be positioned remote from the oil spray, and an ignition element adapted to be arranged in igniting relation to the sprayed oil and having terminals that are adapted to be immersed inthe mercury Wells.

12. An electrical ignition device comprising a mercury well supporting block of insulating material, said block having terminal receiving bores and recesses for' the reception of mercury Wells into which said bores open, metallic mercury Wells having one of `their ends secured within the saidrecesses, means for attaching electrical conductors tothe opposite ends of the wells, and an ignition element having terminals that are adapt- A4 i :momes ed to be extendedjhrough the bores of said block and into the mercury. wells.

, 13. An electrical ignition device comprising a mercury well supporting block of insulating 'ma terial, the block having threaded recesses that open through its lower side and terminal receiving bores that open through its upper side and lead into said recesses, metallic mercury wells threaded at their upper ends for engagement within the recesses of said block, means for attaching electrical conductorsvto thelower ends of said Wells, and an ignition element having terminal posts adapted to be extended through the bores of said block and into the mercury wells.

14. A unitary electrical igniter consisting of as U-.Lhaped Wire resistor, the ends of whose branches are bent laterally and disposed at an acute angle to the plane of theV body portion of said resistor, and terminal posts having axial recesses in one of their Vends into which the ends of the resistor are inserted and wherein they are permanently secured;

15. In a unitary electrical ignition device, an ignition element consisting of a Wire resistor having its ends bent at an angle to its body portion, terminal posts having axial recesses in one ofV their ends into which the ends of the resistor are inserted, and means permanently securing the ends of the resistor in said recesses.

16. A n electrical ignition device consisting of a resistance Wire, terminal posts having recesses in which the ends of the wires are secured, and mercury Wells into which said posts areradapted vto be immersed.

LEE S. CHADWICK. JOHN ALGER-DAHLSTROM. ARTHUR JOHN WILTSHIRE. 

